Question

Which of the following compounds would give addition reactions?

${\mathrm{CH}}_4,{\mathrm{C}}_2{\mathrm{H}}_4,{\mathrm{C}}_2{\mathrm{H}}_6,{\mathrm{C}}_3{\mathrm{H}}_4,{\mathrm{C}}_3{\mathrm{H}}_8,{\mathrm{C}}_4{\mathrm{H}}_{10}$

Answer 1

1. Only unsaturated hydrocarbons undergo characteristic addition reactions.
2. Two types of unsaturated compounds exist with general molecular formula ${\mathrm{C}}_{\mathrm{n}}{\mathrm{H}}_{2\mathrm{n}}$ for alkenes and ${\mathrm{C}}_{\mathrm{n}}{\mathrm{H}}_{2\mathrm{n}-2}$ for alkynes.
3. The given compounds, ${\mathrm{CH}}_4\left(\mathrm{n}=1\right),{\mathrm{C}}_2{\mathrm{H}}_6\left(\mathrm{n}=2\right),{\mathrm{C}}_3{\mathrm{H}}_8\left(\mathrm{n}=3\right),{\mathrm{C}}_4{\mathrm{H}}_{10}\left(\mathrm{n}=4\right)$ satisfy the alkane general formula ${\mathrm{C}}_{\mathrm{n}}{\mathrm{H}}_{2\mathrm{n}+2}$, hence they are saturated hydrocarbons
4. The compound ${\mathrm{C}}_2{\mathrm{H}}_4\left(\mathrm{n}=2\right)$ satisfy the alkene general formula${\mathrm{C}}_{\mathrm{n}}{\mathrm{H}}_{2\mathrm{n}}$ , hence Ethene $\left({\mathrm{C}}_2{\mathrm{H}}_4\right)$undergoes addition reaction with one mole of Hydrogen$\left({\mathrm{H}}_2\right)$ giving corresponding alkane.

$\underset{\left(\mathrm{Ethene}\right)}{{\mathrm{C}}_2{\mathrm{H}}_4\left(\mathrm{g}\right)}+\underset{\left(\mathrm{Hydrogen}\right)}{{\mathrm{H}}_2\left(\mathrm{g}\right)}\stackrel{\mathrm{Ni}/{300}^{\mathrm{o}}\mathrm{C}}{\to }\underset{\left(\mathrm{Ethane}\right)}{{\mathrm{C}}_2{\mathrm{H}}_6}\left(\mathrm{g}\right)$

5. The compound ${\mathrm{C}}_3{\mathrm{H}}_4\left(\mathrm{n}=3\right)$satisfy the alkyne general formula${\mathrm{C}}_{\mathrm{n}}{\mathrm{H}}_{2\mathrm{n}-2}$ , hence Propyne$\left({\mathrm{C}}_3{\mathrm{H}}_4\right)$ undergoes addition reaction with two moles of Hydrogen$\left({\mathrm{H}}_2\right)$ giving corresponding alkane.

$\underset{\left(\mathrm{Propyne}\right)}{{\mathrm{C}}_3{\mathrm{H}}_4\left(\mathrm{g}\right)}+\underset{\left(\mathrm{Hydrogen}\right)}{2{\mathrm{H}}_2\left(\mathrm{g}\right)}\stackrel{\mathrm{Ni}/{300}^{\mathrm{o}}\mathrm{C}}{\to }\underset{\left(\mathrm{Propane}\right)}{{\mathrm{C}}_3{\mathrm{H}}_8\left(\mathrm{g}\right)}$